Nuts for Diabetes Prevention and Management
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Journal of Food and Drug Analysis, Vol. 20, Suppl. 1, 2012, Pages 323-327 ICoFF 323
Nuts for Diabetes Prevention and Management
ALISON KAMIL AND C-Y. OLIVER CHEN*
Antioxidants Research Lab., JM USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA, U.S.A.
ABSTRACT
Type 2 diabetes mellitus is an important preventable disease and a growing public health problem. Epidemiologic and
clinical studies suggest that healthy eating, physical activity, and BW control are the main driving forces to reduce diabetes risk.
Owing to their low available carbohydrate content, favorable fat and protein profile as well as phytonutrient content, nut
consumption has been associated with a reduced risk of development and management of diabetes. Nuts, by virtue of its
cardioprotective actions, have also been shown to reduce biomarkers of risk factors for diabetic complications. Although more
studies are warranted, the emerging picture is that nut consumption beneficially influences diabetes risk and management beyond
blood glucose control.
Key words: Nuts, diabetes, glycemia, body weight, lipids, endothelial function, hypertension, antioxidant, anti-inflammatory
INTRODUCTION of BMI and other risk factors(5). There is also strong evi-
dence for an inverse association between physical activity
The topic of this review is the health benefits of nuts and the risk of diabetes(6).
in diabetes prevention and management. We first provide Healthy eating, physical activity, and BW control are
background information about diabetes. We next discuss the cornerstones of diabetes prevention or management.
nuts as components of a healthy diet for glycemic control The major medical nutrition therapy recommendations
in people with diabetes or at risk for developing diabetes. provided by the American Diabetes Association (ADA)
Finally, as nuts contain a variety of nutrients exerting car- include moderate weight loss and regular physical activity,
dioprotective, antioxidant, and anti-inflammatory actions, with dietary strategies including reduced calories and in-
we will present studies demonstrating how nuts could take of dietary fat. Recommended foods include: healthy
ameliorate biomarkers of risk factors for diabetic compli- CHO such as whole grains, fruits, vegetables, legumes,
cations. and low-fat dairy; heart healthy fish; good fats high in
monounsaturated (MUFA) and polyunsaturated fatty acids
DIABETES INCIDENCE AND MANAGEMENT (PUFA). Foods to limit include: bad fats high in saturated
(SFA) or trans-fatty acids; sodium; and alcohol(7). Hence,
Diabetes is characterized by hyperglycemia and glu- the application of nutritional therapy to lower the risk or
cose intolerance due to insulin deficiency and/or impaired delay the onset of diabetes is important.
effectiveness of action. As of 2007, roughly 6% were af-
fected worldwide and it is estimated that this will increase NUTRITION COMPOSITION
to 7.3% by 2025(1). Fueled by rapid urbanization, nutrition
transition, and increasingly sedentary lifestyles, Asia ac- “Tree-nuts” or nuts are a nutrient dense food that
counts for 60% of the world’s diabetic population(2). Type contains diverse macro and micronutrients and other phy-
2 diabetes mellitus (T2DM) is by far the most common tochemicals that may have beneficial effects on T2DM and
disorder, affecting 90 - 95% of the U.S. diabetes popula- other health complications(8). Nuts are rich in magnesium,
tion(3). which helps regulate blood sugar levels and is involved in
Several factors contribute to the development of energy metabolism. Nuts are also a good source of dietary
T2DM, including family history, ethnicity, age, genetics, fiber which decreases gastric emptying, in turn decreasing
lifestyle, diet, and body weight (BW). Excess BW, par- the rates of CHO breakdown and glucose absorption. Fur-
ticularly abdominal adiposity is the most important modi- thermore, nuts are high in unsaturated fats, mostly high in
fiable risk factor for development of diabetes. The inci- MUFA in most nuts and PUFA in walnuts. Their unsatu-
dence of diabetes clearly rises as obesity prevalence in- rated fats appear to exert anti-inflammatory and lipid low-
creases(4,5). Furthermore, diet quality especially of fats and ering effects. L-arginine is also an important constituent of
carbohydrates (CHO) play an important role, independent nuts that is essential to vascular function. Nuts contain an
*
Author Correspondence. Tel: 617-556-3128;
Fax: 617-556-3344; Email: Oliver.Chen@tufts.edu324 Journal of Food and Drug Analysis, Vol. 20, Suppl. 1, 2012
array of phytonutrients, e.g., carotenoids, phenolics, and low fat diets (≤ 20% kcal) have been shown to have poor
phytosterols, which exert antioxidant and an- adherence in the outpatient treatment of obesity(16), alter-
ti-inflammatory actions as well as an inhibitory effect on native approaches with more moderate fat content (35%
starch digestive enzymes. Incorporation of nuts into a diet kcal, < 10% from SFA) which increases palatability may
may therefore improve the overall nutritional quality of the enhance compliance to weight loss diets. Wien et al. re-
diet. ported reductions in BW, BMI, waist circumference, and
fat mass being 62, 62, 50, and 56% greater, respectively,
than the control diet. The above lack of effect of nut con-
NUTS AND DIABETES PREVENTION sumption on weight gain could be attributed to the ob-
served calorie displacement from other foods, satiating and
Jiang et al.(9) observed in the Nurses’ Health Study palatability properties of nuts, and the probable modest
that women consuming a 1 oz serving of nuts >5 times/wk malabsorption of nut fats(17). Thus, nuts could be a part of a
had a 25% lower risk of developing T2DM compared with balanced, healthy diet for glycemic and BW management.
women who never ate nuts. Recently, the PREDIMED
study(10) with 418 persons at high cardiovascular risk
showed that a traditional high-fat Mediterranean diet en- NUTS AND DIABETES MANAGEMENT
riched with mixed nuts (30 g/d) or olive oil decreased the
incidence of diabetes by 50% after a median follow-up of According to the ADA, the primary objective in
4 yrs compared to a control diet consisting of advice on a management of diabetes is achievement of targeted glyce-
low-fat diet. mic control (HbA1C < 7%)(18). Besides the acute trials
Owing to their low available CHO content and fa- above showing reductions in postprandial glycemia in in-
vorable fat profile, nuts may decrease the risk of diabetes dividuals at risk for development of T2DM, up to date
by reducing postprandial blood glucose levels. This is im- there are 4 clinical trials demonstrating the effect of nuts
portant as chronic hyperglycemia causes damage to the on glycemic control in T2DM patients. Cohen & Johnston
eyes, kidneys, nerves, and blood vessels. Kendall et al.(11) (19)
reported in a 12 wk randomized crossover trial with
examined the effect of pistachios on postprandial glycemic T2DM patients that consumption of 28.4 g/d almonds at a
response, in a two stage study with 10 healthy overweight frequency of 5 d/wk decreased HbA1c as compared to a
subjects. Addition of pistachios to 50 g available CHO control diet without almonds (4% reduction vs. 1% in-
resulted in a significant reduction in the glycemic response crease, respectively). Li et al.(20) demonstrated in a ran-
of the composite meal in a dose-dependent manner for the domized, crossover, controlled trial that almonds (60 g/d)
28 g (5.7%), 56 g (3.8%), and 84 g (9.3%). Likewise, ad- replacing 20% calories of the control National Cholesterol
dition of 56 g pistachios to CHO foods significantly at- Education Program (NCEP) Step 2 diet significantly de-
tenuated their glycemic response: parboiled rice (19%) and creased fasting blood glucose and insulin and HOMA in-
pasta (40%). Similarly, Josse et al.(12) found that the addi- sulin resistance as compared to the control diet. After a 42
tion of almonds to white bread with 50 g CHO resulted in wk intervention with an almond-based, high fat and pro-
a progressive reduction in the glycemic index of the com- tein diet (40, 22, and 25% kcal from fat, MUFA, and pro-
posite meal in a dose-dependent manner for the 30 g tein, respectively) vs. a contemporary American Heart As-
(105.8), 60 g (63.0), and 90 g (45.2) in 9 healthy volun- sociation diet (30, 15, and 15% kcal, respectively) in 17
teers. Furthermore, since the nutrient bio-accessibility of patients with metabolic syndrome or T2DM, Scott et al.(21)
nuts consumed in different physical forms might be dif- noted that the former diet was modestly better in glycemic
ferent, Mori et al.(13) reported in a randomized crossover control. Jenkins et al.(22) reported in a 3 mo randomized
trial with 14 patients with impaired glucose tolerance (IGT) parallel study with 117 T2DM subjects that supplementa-
that 42.5 g whole almonds, but not comparable amounts of tion with mixed nuts (75 g/d) to a 2,000 kcal diet in re-
almond butter or defatted almond flour, added to a 75 g placement for CHO foods significantly reduced HbA1c
available CHO-matched meal decreased postprandial glu- 21% compared to supplementation with half-nut dose or
cose response compared to a no almond vehicle. muffin. Hence, frequent nut consumption has a beneficial
Given the rapidly increasing obesity prevalence, nuts effect for blood glucose control in T2DM patients as part
may decrease the risk of diabetes through weight man- of a strategy to improve diabetes control.
agement. Bes-Rastrollo et al.(14) reported in the Nurses’
Health Study II with an 8 yr follow-up that women eating
nuts >2 times/wk had slightly less mean weight gain (5.04 BENEFITS BEYOND GLUCOSE CONTROL
kg) than did women who rarely ate nuts (5.55 kg). More-
over, Wien et al.(15) assessed the effect of an al- Diabetes is associated with a myriad of other health
mond-enriched (84 g/d) or complex-CHO-enriched low complications that include cardiovascular disease (CVD),
calorie diet (1012 kcal/d) on anthropometric, body compo- hypertension, cancers, and renal and gallstone disease.
sition and metabolic parameters in a randomized prospec- More specifically, of these patients with diabetes or IGT,
tive 24 wk trial with 65 overweight and obese subjects. As 75% will die of some form of CVD(23). Thus, the expandedJournal of Food and Drug Analysis, Vol. 20, Suppl. 1, 2012 325
goals of diabetes management, besides slowing or stopping compared to isocaloric pork (120 g/d). They also demon-
disease progression, must include optimizing the reduction strated that adding almonds led to increased activities of
of all risk factors associated with disease complications. A serum superoxide dismutase and glutathione peroxidase,
pooled analysis of epidemiologic studies shows a clear but not changed after pork. Inflammation also plays a crit-
dose response between nut consumption and a reduced risk ical role in the risk for and progression of CVD and T2DM
of coronary heart disease (CHD)(24). Collectively, these such that biomarkers like C-reactive protein (CRP) and
findings provide compelling evidence of the cardioprotec- interleukin-6 (IL-6) are independent predictors of their
tive benefit of nut consumption. pathology. An anti-inflammatory action by nuts is consis-
Dietary intervention studies have shown that nut con- tent with the observation that frequency of nut and seed
sumption can reduce the risk of heart disease by improving consumption is inversely associated with each of these
serum lipid profile, endothelial function and blood pres- biomarkers(31). In a randomized, controlled, crossover
sure, in addition to lowering oxidative stress and inflam- clinical trial with healthy adults, Rajaram et al.(32) found
mation. A pooled analysis of 25 intervention studies(25) incorporating almonds into the diet at 10 and 20% of calo-
evaluating the effect of nuts on blood lipids among people ries (34 and 68 g/2000 kcal, respectively) for 4 wks low-
with normolipidemia and hypercholesterolemia, demon- ered CRP compared to a nut-free control diet, although no
strated significant reductions in both total cholesterol dose-response relationship was observed. E-selectin, a cell
(5.1%) and LDL-C (7.4%) with a mean daily consumption adhesion molecule activated by cytokines during inflam-
of 67 g of nuts and greatest among subjects with high mation, was also significantly lower, but only with the
LDL-C or with lower BMI consuming Western diets. higher almond dose. These results suggest that nuts can
Moreover, walnuts are the only nuts that have been for- enhance antioxidant defenses and diminish inflammation
mally studied for effects on endothelial function, which is and oxidative stress. More studies are warranted to eluci-
important as endothelial dysfunction has been shown to be date the mechanism of actions for these reductions in bio-
predictive of future adverse cardiovascular events. In a markers.
randomized, controlled crossover trial with 24 participants
with T2DM(26), endothelial function as measured by
flow-mediated dilation (FMD) was significantly improved CONCLUSION
after consumption of a walnut enriched diet (56 g/d) com-
pared to a control diet without walnuts (2.2 vs. 1.2%, re- The available data demonstrate that nuts as replace-
spectively). Similarly, Ros et al.(27) demonstrated in a ran- ment for CHO have beneficial effects on diabetes risk and
domized crossover design with 21 hypercholesterolemic management. In general, the nutrient composition of nuts
subjects that replacement of ~32% of the energy with and emerging clinical evidence provide a strong justifica-
walnuts significantly improved FMD compared to a con- tion in support that they could be a part of a balanced,
trol diet without walnuts with a similar energy and fat healthy diet for glycemic, BW management, and cardio-
content. Further studies are needed to confirm that overall protection. More research with robust study designs are
nut intake influences endothelial function. To note, few needed to better identify differential effects of different
studies have examined the effect of nut consumption on types of nuts as well as the benefits in the longer term.
incidence of hypertension. However, the result of the Phy-
sicians’ Health Study I showed there was an inverse rela-
tion between nut intake and hypertension among U.S. male
physicians (BMI < 25)(28). Further examination of the rela-
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DNA damage and lipid peroxidation in maleYou can also read
